As a production (synthesis) method of nucleic acids such as DNA, RNA and the like, for example, a phosphoramidite method and the like are used. As a starting material for the nucleic acid synthesis by the phosphoramidite method, phosphoramidite of nucleoside (hereinafter to be simply referred to as “phosphoramidite”) is used. Examples of the protecting group at the 2′-position of the aforementioned phosphoramidite include many protecting groups such as TBDMS (tert-butyldimethylsilyl) group, TOM (triisopropylsilyloxymethyl) group, ACE (bis(2-acetoxyethoxy)methyl) group and the like.
However, since the production cost of conventional phosphoramidites such as TOM amidite, ACE amidite and the like is high, they are not convenient as starting materials for the synthesis of pharmaceutical products and the like. In addition, the yield and purity of nucleic acid are sometimes not very high when nucleic acid is synthesized by a coupling (condensation) reaction using TBDMS amidite.
Thus, the development of a protecting group capable of providing a phosphoramidite which can be produced at a low cost and can produce a nucleic acid in a high yield with high purity has been tried (patent documents 1 and 2).